A manipulator is used for an arm of a robot in a logistics or production site to perform works for holding a load or a produced component and moving the load or the produced component to another location.
The manipulator uses a deadweight compensation mechanism capable of cancelling the weight of the manipulator itself (i.e., the deadweight) with a mechanical structure. With this deadweight compensation mechanism, a power for maintaining the static state of the manipulator can be reduced.
In a conventional design of a manipulator, a method in which a torque motor for driving a joint of a manipulator is provided at an outside of the joint or a method for using a weight to balance moments about a rotation axis of a joint of a manipulator are employed to cancel a deadweight of the manipulator. Therefore, the energy consumed by a torque motor can be reduced. Since it is not necessary to have a large torque motor, the manipulator can be reduced in size. However, there is no deadweight compensation mechanism made in view of a mass of an object held by a holder of a manipulator. It is desired to achieve a compact manipulator that includes the deadweight compensation mechanism in view of a mass of an object held.